70mm Headphone Replacement Foam Earpads, Bag of 4 Each bag contains 4 Replacement 70mm Size Foam Earpads, enough for 2 pairs of headphones. Measure the size of your earpiece from edge-to-edge and find the foam earpad that is between the range of your measurement. Remove the existing foam and stretch the new sponge foam cushion onto your headphone earpiece. If your earpiece is oval shaped, just determine the average size by adding the width plus the height (edge-to-edge measurement of earpiece) and divide by 2. The 70mm foam earpads fit most headphones and headsets with an earpiece diameter between 2.19 inches to 2.5 inches (or 55mm to 63.5mm) in average diameter. You can convert inches to millimeters by multiplying by 25.4. For example, if your earpiece is 2  inches, just multiply 2.5 x 25.4 and you will get 63.5mm.